The Difference between XRF and ICP?

The Difference between XRF and ICP?

When it comes to converter toll-refining, how does ICP differ from XRF analysis when determining value?

ICP and XRF can provide Accurate Readings

Toll-Refining Is When The Owner Of A Commodity Contracts The Refining Of A Metal To Another Party For A Fee, But The Refined Metal Remains Under The Original Ownership For Final Sale Or Disposition.

Although there are multiple methods used in the analysis of recycled catalytic converters, the two predominant technologies handled by toll-refiners are benchtop X-Ray Fluorescence machines (also referred to as an XRF machine) and Inductive Coupled Plasma machines (also referred to as an ICP machine). If handled correctly and with an appropriate sample, both ICP and XRF provide accurate readings.

XRF & ICP Instruments Determining Value

– XRF is a non-destructive analytical technique used to determine the elemental composition of materials. A loose homogenous powder sample is prepared and put into a cup to be placed in the XRF analysis chamber and is then scanned. A report is then produced indicating the elements that were detected within the sample. Depending on the XRF model, analysis can take minutes to hours.

-When ICP is used for analysis, a homogenous powder (sample) is converted into a liquid sample and elements contained within that sample are separated. A plasma flame is then used to make the elements visible enabling relevant precious metal contents can then be identified. This method is both a chemical and fire assay.

Now begs the age-old question, how do both differ when it comes to determining value? An even more prevalent question within industry is which instrument is better for accurate analysis?

When considering a method of analysis, a toll-refiner is always considering three components. In most cases,only two of the three components can be chosen when using any one analytical instrument. Those components are accuracy, time, and investment.

XRF machines require minimal sample preparation, a lower financial investment and produce a relatively fast analysis. Although this method may not be as accurate as ICP, accuracy is heavily determined by sample preparation and proper calibration. Therefore, with the proper sample – which means having the correct particle size and homogeneity, as well as proper machine calibration, the accuracy can still be very precise. ICP machines are a big capital investment; they require good analytical chemistry skills for sample preparation. Excellent accuracy is, however, a top benefit – although it should be noted, that this accuracy also comes at the expense of time.

Robust laboratories and toll-refiners will use multiple methods, as it is common to conduct preliminary analyses for a quick assessment of value as well as final analyses for confirmed accuracy. The time to conduct such analyses will differ across laboratories.

ICP & XRF Instruments Provide Accurate Readings, IF…

The bottom line is both instruments provide accurate platinum group metal (PGM) readings IF the sample used for the analysis was prepared correctly.

Samples need to be ground into fine particles with a consistent mesh rate for good results. Humidity also needs to be measured in each sample as it will affect the weight of the material. Both ICP and XRF machines should be calibrated daily.

To conclude, sample preparation is extremely important in determining value, and if not handled appropriately, the consequence will be inaccurate results, regardless of the analytical method chosen.

For more evaluation and processing knowledge, visit PMR’s Resource Center.

Published: September 1, 2022
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